I prefer sims 3 because there's a lot more mods, cc, and expansions out for it. I like the open world more than seeing loading screens for every location.
I've mentioned it before but I barely want to open sims 4 and it's too kid-friendly. The sims smile too often and nothing bad really happens. They just enjoy their happy little world but I want destruction and chaos so I'm bored with it. The closest I have to it is the cursed painting mod that kills sims if they don't win the 1000 simoleons. I'm capable of making good looking sims in both games so I'm not comparing graphics. Many people like sims 4 sims looks but the game itself doesn't have much going for it.